This application will study the biology of IL-13 and two new CC chemokines, C10 and MDC in the pathogenesis of sepsis following cecal ligation and puncture (CLP) in mice. Cytokine networks are critical in the host response to peritonitis and other forms of sepsis. The major hypothesis is that during the evolution of sepsis, IL-13 and CC chemokines induced by IL-13 regulate the host response and protect the host from organ injury. This hypothesis will be explored in 4 specific aims using a murine model of cecal-ligation and puncture (CLP) in mice. Aim 1 will investigate the expression and tissue distribution of IL-13. Aim 2 will investigate the role of IL-13 in the pathogenesis of sepsis using several different strategies to neutralize IL-13. Aim 3 will investigate the expression and role of MDC and C10 in sepsis using methods similar to those in Aims 1 and 2. Aim 4 will use transgenic mice to explore the role of STAT6 as a key signaling molecule in the pathogenesis of sepsis in CLP. These studies will provide new information about the key roles of IL-13 and CC chemokines in the pathogenesis of the systemic response induced by CLP in mice.